4.2.6.1 Hash tables, hashing and collisions Quiz: AQA Computer Science, Unit 2

The 20 questions

1. Which data structure creates a direct mapping between key values and stored values?

   • Binary tree
   • Hash table
   • Queue
   • Priority queue

2. What converts a key into a specific storage index in a hash table?

   • Index pointer
   • Hash function
   • Key mapper
   • Search algorithm

3. What occurs when a hash function generates the same index for two different keys?

   • Underflow
   • Deadlock
   • Collision
   • Overflow

4. Which process finds an alternative slot in a hash table when a collision occurs?

   • Sorting
   • Indexing
   • Truncating
   • Rehashing

5. A hash function is key MOD 7 and the table has 7 slots (0 to 6). Where is the key 23 stored?

   • Slot 3
   • Slot 5
   • Slot 2
   • Slot 0

6. Using the hash function key MOD 7, to which slot index does the key 17 hash?

   • 4
   • 3
   • 2
   • 1

7. A hash table of 10 slots uses key MOD 10. Which slot does the key 47 use?

   • 47
   • 0
   • 4
   • 7

8. A hash table has 11 slots and uses key MOD 11. Which key below would hash to slot 0?

   • 13
   • 9
   • 23
   • 22

9. What is the primary purpose of spreading keys evenly across a hash table?

   • Eliminate pointers
   • Sort key values
   • Reduce memory size
   • Minimise collisions

10. Which hash table operation executes in O(1) average time when collisions are minimal?

    • Sorting keys
    • Finding minimum
    • Key lookup
    • Full traversal

11. Which collision resolution method checks consecutive slots sequentially until an empty slot is found?

    • Binary search
    • Chaining traversal
    • Depth-first search
    • Linear probing

12. Using linear probing with step 1, where is a key hashing to occupied slot 4 placed?

    • Slot 0
    • Slot 6
    • Slot 3
    • Slot 5

13. Which property ensures a hash function distributes keys uniformly across all available slots?

    • Sequential ordering
    • Inverted indexing
    • Uniform distribution
    • Reversible mapping

14. Which data structure is most commonly used to implement an abstract dictionary data type?

    • Queue
    • Stack
    • Hash table
    • Linked list

15. Which slot do keys 5, 13, and 21 all hash to using the calculation key MOD 8?

    • Slot 0
    • Slot 7
    • Slot 3
    • Slot 5

16. What component maps a key to a valid storage index within a hash table?

    • Hash function
    • Index vector
    • Search tree
    • Pointer array

17. Which index do keys 12 and 27 both compute using the hashing algorithm key MOD 5?

    • Index 2
    • Index 5
    • Index 0
    • Index 1

18. What is a key disadvantage of a hash table compared with a sorted array?

    • Higher time complexity
    • Greater memory usage
    • Unordered data
    • Slower searching

19. What is the best way to resolve frequent collisions in a nearly full hash table?

    • Truncate all keys
    • Clear the table
    • Resize and rehash
    • Sort the table

20. Which mathematical operation is most commonly used in simple hashing algorithms?

    • Square root
    • Logarithm
    • Modulo
    • Factorial

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